NORMAN, Okla. — A packed house was rocking and the game hadn’t even started yet when Kansas State and Oklahoma players had to be separated and steered toward their own sideline. Once the Sooners took control in a clash of top 15 teams, the K-State fans started booing and stuff came flying out of the stands.

The Big 12 rivals meet again today, again with high stakes, but this time on Oklahoma’s home field.

“It’s a challenge. You’re either going to step up to it or you’re not,” Sooners linebacker Tom Wort said. “Last year, even before the game, you could tell that both teams wanted to go at it. We were at each other in the end zone.

“It’s going to be a lot of fun. It’s that kind of game. Not in any dirty way, but you’re going to try to break the other person.”

The Wildcats were off to a 7-0 start, ranked 10th and dreaming big when Oklahoma paid a visit late last October for homecoming. The Sooners were steaming after their own undefeated run had been snuffed out at home by Texas Tech, ending their 39-game winning streak on Owen Field.

The top 15 showdown comes a month earlier this year, but with both teams harboring high hopes. The Sooners are ranked sixth, with K-State at No. 15.

“It’s a high-level opponent. You’ve got to be more ready for something like this,” Wort said. “With a big game, a home game, against a ranked team, it’s going to be a good atmosphere. You’ve got to be excited for it.”

With some goading, coach Bob Stoops even put the pressure on Oklahoma fans to bring their best game. All 81 home games have been sellouts while Stoops has been coach, but the noise factor hasn’t always been there like the last time Stoops issued a challenge for a top-five showdown against Texas Tech in 2008.

“You’d like to see them like that every Saturday, but if you can’t be every Saturday, hopefully you will be this Saturday,” Stoops said. “How’s that?”

The Wildcats’ faithful were certainly in full throat for last year’s meeting, which ended with No. 11 Oklahoma scoring the final 44 points in a 58-17 blowout.

“They were crazy. They were so hostile,” Oklahoma linebacker Corey Nelson said. “The environment was very hostile. I just remember them throwing ice at us after we was beating them, and they were throwing hot dogs at us as well.”

Nelson and the Sooners did their part to instigate the animosity.

On the final play of Kansas State’s drive to open the second half, defensive end Frank Alexander tackled quarterback Collin Klein for a loss and then stepped on his chest. No flag was thrown, with Alexander saying it was an accident, and the Wildcats punted.

The next K-State drive ended with Nelson bumping Klein after he had stepped out of bounds, then grabbing him to soften the blow as Klein crashed into a metal bench. This time, a flag was thrown but officials met and decided not to assess a penalty.

“The fans just went nuts,” Nelson recalled.

Heading into what could be a madhouse that’s against them this time, Klein said the Wildcats can’t focus on the sideshow.

“Like coach says all the time, ‘Keep the game in between the white lines.’ You focus on what we can control and not getting involved in anything that doesn’t have to do with that,” he said.

“Ultimately, it’s going to come down to discipline and toughness. Who’s more disciplined to do what they plan to do and do it consistently through the whole game? That’ll be it.”

The sour memories haven’t faded entirely, though.

Kansas State had rallied from a 14-0 deficit with 17 straight points when it all came unraveled last season. The questionable plays by Alexander and Nelson came just as the game was turning in the opposite direction.

“I think a lot of things didn’t happen is probably the best way to sum that up,” Klein said. “We quit moving the ball, that put a tremendous amount of pressure on our defense when they have a great offense and it just kind of snowballed.

The Sooners, a perfect 14-0 against ranked teams at home under Stoops, know they had better be ready for a vengeful Kansas State team that has lost five in a row in the series, none more painful than last season.

“We kind of got after them a little bit last year, and that doesn’t leave. When somebody comes into your house and does you like that, that stays with you,” Oklahoma defensive lineman David King said.

“I’m sure their coaches are preaching to them, ‘They did this to us’ and they’re just going to try and come in here and do what we did to them last year.”